(CNN) -- This month we're on the trail of the modern adventurers who risk their lives in the name of discovery.

Quest and crew on location in Tibet.

In today's high-tech age, science has all but exhausted our planet's secrets. It's a far cry from the golden age of exploration, when daring men set sail into the unknown, fearful they might suddenly drop off the edge of the world.

The achievements of trailblazers like Vasco da Gama, James Cook or Christopher Columbus can never be surpassed, so some might argue that real explorers are a thing of the past... adrenalin junkies with nothing left to search for?

In this episode, Richard Quest finds out what motivates today's hardy crop of explorers and uncovers the madness that drives them to boldly go where no one has gone before.

We start in the English countryside, on a sheep farm, owned and operated by Sir Ranulph Fiennes. From the White Nile to the lost city of Ubar in Oman, this formidable individual has led expeditions all over the world since the 1960s.

He was the first man to visit both the North and South Pole by land and the first to completely cross the Antarctic by foot. "The greatest living explorer" according to the Guinness World of Records, the undisputed king of narrow escapes, reflects on his life at the edge of reason -- and what it's like to lose your fingers to frostbite.

We've sent more people to the moon than the deepest parts of the ocean. Eighty percent of life on Earth, the deepest valleys, the tallest mountains -- it's all underwater but we've only seen five percent of what's out there.

Quest travels to the Monterey Bay Marine Sanctuary to meet the lady they call "Her Deepness". Dr Sylvia Earle is an explorer in residence for National Geographic, honorary director of the Explorers' Club and has led more than 60 expeditions worldwide.

Having logged over 6,000 hours underwater, she is a seasoned aquanaut and even holds the record for the deepest untethered solo dive, at a depth of 1,000m.

Surrounded by whales and dolphins, Quest soon succumbs to Earle's infectious enthusiasm and insatiable thirst for knowledge through exploration.

Next up, Quest finds himself in the principality of Monaco for a very royal tale of exploration. In the 1800s, Prince Albert I left behind an extraordinary wealth of knowledge from a lifelong interest in the then new science of oceanography.

He pioneered new techniques and explored the oceans alongside the leading marine scientists of his day -- he also founded what would become the world renowned "Oceanographic Institute" in Monaco.

Armed with an invite to the palace, Richard interviews Prince Albert II about his great-grandfather's legacy and his own recent voyage to the North Pole.

The Swiss Alps -- the epitome of the great outdoors and the perfect terrain for a great explorer to train his mind, body and soul. It is here that we meet South African Mike Horn who entered the exploration hall of fame in 1999 when he became the first person to circumnavigate the world, along the equator.

Horn has sailed the seas, traveled the length of the Amazon and walked to the North Pole during the Arctic winter. So who better to put Richard through his paces and teach him what it takes to prepare for a serious expedition?

Pulling three heavy tires up a rocky canyon, with the words, "No pain, no gain," ringing in his ear, Quest assesses the fine line between the adventurer, the explorer and the extreme athlete.

Finally, with his rucksack full to the brim, Richard Quest travels in the footsteps of Marco Polo to the Himalayan valleys and peaks of Tibet. At his side is Wong How Man, president of the China Exploration and Research Society.

In 2002 Time Magazine chose How Man as one of its 25 Asian Heroes, calling him "China's most accomplished living explorer." So when it comes to keeping Quest from falling off a mountain... if anyone can, How Man can!

Negotiating high-altitude terrain, on horseback, the expedition team wind their way up to a remote monastery high above the tree line.

With none of the luxuries he knows and loves, this is a chance for Quest to pit his wits against the elements, try out his new outdoor gear and feel what it's like to venture into uncharted territory. Dramatic scenery, extraordinary sights and sore feet guaranteed!

Satellites beam back pictures from above and it's true that the surface of our planet has been comprehensively mapped. It's undeniable that the great romantic journeys have all been done -- but does Quest have what it takes to make his personal mark on the field of human exploration?E-mail to a friend